NSFetchedResultsController不适用于sectionNameKeyPath的瞬态属性 [英] NSFetchedResultsController not working with transient property for sectionNameKeyPath
问题描述
在Swift 3中使用Xcode8.3可以正常工作
我正在进行一个项目,该项目具有用于保存消息的核心数据。
它根据时间对消息进行排序,并根据天对消息进行分段。 = NSFetchRequest(实体名称:消息)
let sortDiscriptor = NSSortDescriptor(键:时间,升序:正确)
request.sortDescriptors = [sortDiscriptor]
fetchedResultsController = NSFetchedResultsController(fetchRequest:request,managedObjectContext:mainThreadMOC,sectionNameKeyPath: sectionTitle,cacheName:nil)
fetchedResultsController.delegate =自我
做{
尝试fetchedResultsController.performFetch()
} catch {
fatalError(未能初始化FetchedResultsController:\(错误))
}
这是临时属性:
var sectionTitle:字符串? {
//这是** transient **属性
//将其设置为瞬态,请在数据模型
返回时间中选中具有相同名称的框!.getTimeStrWithDayPrecision()
}
将其用作:
func tableView(tableView:UITableView,numberOfRowsInSection部分:Int)-> Int {
let sectionInfo = fetchedResultsController.sections![section]
let n = sectionInfo.numberOfObjects
return n
}
它始终提供0个部分,而 sectionTitle
属性永远不会被调用。
此设置在Xcode8.3中与Swift3一起正常工作。
即使在Xcode9-beta中与Swift3.2一起工作。
但是,如果我在Xcode9-beta中切换到Swift4,它不起作用。
在临时属性中添加@objc,因此:
@objc var section标题:字符串? {
//这是** transient **属性
//将其设置为瞬态,请在数据模型
返回时间中选中具有相同名称的框!.getTimeStrWithDayPrecision()
}
Working fine in Swift 3 with Xcode8.3
I have a project ongoing which has core data for saving messages.
It sorts messages according to time and sections them according to day.
Here's how:
let request = NSFetchRequest(entityName: "Message")
let sortDiscriptor = NSSortDescriptor(key: "time", ascending: true)
request.sortDescriptors = [sortDiscriptor]
fetchedResultsController = NSFetchedResultsController(fetchRequest: request, managedObjectContext: mainThreadMOC, sectionNameKeyPath: "sectionTitle", cacheName: nil)
fetchedResultsController.delegate = self
do {
try fetchedResultsController.performFetch()
} catch {
fatalError("Failed to initialize FetchedResultsController: \(error)")
}
Here is transient property:
var sectionTitle: String? {
//this is **transient** property
//to set it as transient, check mark the box with same name in data model
return time!.getTimeStrWithDayPrecision()
}
Using it as:
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
let sectionInfo = fetchedResultsController.sections![section]
let n = sectionInfo.numberOfObjects
return n
}
It always gives 0 sections and sectionTitle
property never getting called.
This setup was/is working correctly with Swift3 in Xcode8.3.
Even this is working with Swift3.2 in Xcode9-beta.
But if I switch to Swift4 in Xcode9-beta, it's not working.
Add @objc to the transient property, so:
@objc var sectionTitle: String? {
//this is **transient** property
//to set it as transient, check mark the box with same name in data model
return time!.getTimeStrWithDayPrecision()
}
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